“In the early stages (presolicitation) of the SCAR program, the draft requirement defined a single weapon platform capable of adapting to multiple calibers (i.e. 5.56×45 mm, 7.62×51 mm, and 7.62×39 mm). FN had proposed and offered a single-platform system to USSOCOM that would adapt via conversion kit to SOF current and future ammunition. During the requirements finalization phase, the SOF operators took the decision that the weapon should be split in two platforms, one gun for 5.56 and a second gun for 7.62. The reason this decision was made at the time is that the SOF operators did not like the fact that the 5.56 base platform would have an increase in weight over the M4. The weight difference between the MK 16 Standard and the SCAR H Standard is about half a pound. Upon completion of the developmental test (DT), the operation test (OT), and the full Fielding and Deployment Release (FDR) authorization, AKA Milestone C, a new group of operators reversed that initial decision and said that they wanted to move back to the original spirit of the program: a single weapon platform capable of converting between 7.62 and 5.56.

Basically, to accomplish a multi-caliber system requires that we develop the gun on the basis of the largest caliber and then scale down the conversion kit to go to a smaller caliber. The MK 17 receiver is a little larger to accommodate the 7.62×51 mm ammunition. It is not possible to scale up a smaller receiver to accept 7.62 ammunition, thus the MK 17 was chosen as the base platform. This was almost seven years after the initial decision to split the platform and a new group of operators had rotated into the SCAR program effort. FN finalized the 5.56 conversion kit in late 2010 and it has passed all DT and OT testing, and an initial delivery order has been placed for the conversion kit.”

The problem with SCAR is that when you swap barrels, even within the same caliber, you have to re-zero your optics, no matter what they tell you. This is why I personally prefer the Colt CM901 AR-format rifle/carbine/SBR, which is truly modular in the sense that when [you] swap uppers (upper receivers), you can have your optics already pre-zero’d to them, so it’s swap-and-go. No re-zeroing required.

All the SOF assaulters/operators I’ve spoken with prefer swapping the whole upper with pre-zero’d optics as one unit.”

While Defense Review prefers the Colt CM901/SP901 modular, multi-caliber AR platform with universal lower receiver concept, Defense Review still likes the FN MK17 SCAR-H (SCAR-Heavy) and its multi-caliber upper receiver/semi-quick-change barrel concept, provided the MK-17’s relatively thin extruded aluminum receiver and thin-profile barrel can hold up to both the 7.62x51mm (7.62mm NATO)/.308 Win. caliber at high round count and adverse combat envirornments, which has yet to be proven. The FN MK-17 SCAR-Heavy may indeed have some legs with SOF forces and SOCOM procurement, and competition between the MK17 and CM901 is a healthy thing. Let the best gun/weapons platform win.

About David Crane

David Crane started publishing online in 2001. Since that time, governments, military organizations, Special Operators (i.e. professional trigger pullers), agencies, and civilian tactical shooters the world over have come to depend on Defense Review as the authoritative source of news and information on "the latest and greatest" in the field of military defense and tactical technology and hardware, including tactical firearms, ammunition, equipment, gear, and training.